Typically, a keyboard used as a user input device for an application resident on a data processing system, e.g., a program running on a personal computer (PC), a personal digital assistant (PDA) or the like, includes electronic circuits which scan a matrix of switches actuated by the keys to determine the row and column of the depressed key. The row and column values then are mapped to a corresponding binary keycode which may then be transmitted to the data processing system. The keycode may be communicated from the user input device to the data processing system via wires, radio signals, infrared signals and other communication techniques. Keycodes may be standardized, such as the standard codes used to communicate between keyboards and PCs to ensure compatibility.
Although keyboard data entry is commonly used in data processing systems such as desktop and portable PCs, it may also be desirable for smaller portable devices such as PDAs and portable intelligent communicators (PICs). Both wired and wireless interfaces may be employed between a user input device and the data processing system. In portable devices such as PDAs and PICs, and in wireless keyboard applications for desktop or portable systems, power consumption may be a critical issue, as portable systems and wireless user input devices typically are battery-powered to increase their portability. Accordingly, these devices tend to be limited by the energy storage capability of the batteries used in the devices.
A typical keyboard entry application such as a word processor can involve processing of a large number of keystrokes in a short period of time. Accordingly, a large number of keycodes may need to be transmitted in a short time, which can lead to significant energy consumption in communicating between the keyboard and the application. For example, a wireless infrared keyboard typically transmits keycodes by modulating an infrared transmitter which is powered by a battery or similar power source included in the keyboard. The infrared transmitter typically consumes significant power when it is illuminated or "on." If the transmitter is frequently on, a greater amount of battery power may be consumed. In addition, high frequency switching of components which drive the transmitter may increase energy consumption by the keyboard. Accordingly, generation of a stream of keycodes which requires the infrared transmitter to be on for significant periods of time and which requires frequent switching of the transmitter can quickly exhaust the power source of the keyboard. Accordingly, there is a need for more energy efficient systems and methods for communicating user inputs from portable input devices such as wireless keyboards.